University of Minnesota
School of Physics & Astronomy

High Energy Theory Lunchtime Seminar

Friday, March 3rd 2017
Speaker: Ryo Namba (McGill)
Subject: Gravitational wave signals from low-energy inflation

Detection of tensor mode fluctuations at the largest cosmological scales is often expected to provide a robust evidence of inflation and to fix the inflationary energy scale. Such direct connection is however applicable only when the tensor perturbations are originated from their quantum fluctuations during inflation and are effectively decoupled from other energy contents. We consider a case exceptional to this lore. When an SU(2) gauge field is present and is prevented from diluting away by a coupling to a pseudo-scalar, the configuration of the SU(2) vev preserves the background isotropy, and on this geometry, the SU(2) perturbations introduce an additional tensor mode. The substantial growth experienced by this mode is then transferred to the true tensor fluctuations of the metric already at the linear level. While these fields are energetically subdominant to the inflaton, their perturbations can be considerably larger than the standard amplitude. We discuss several potential constraints on the mechanism and demonstrate that detectable tensor mode signals even for low energy inflation.

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